The Conservatives shrugged off fresh criticism of David Cameron yesterday as another of the party’s largest donors voiced dissatisfaction with his leadership.

Sir Tom Cowie, who has given the party more than £630,000 over the past six years, said he had stopped providing financial support to the Tories and accused Mr Cameron of “arrogance”. He was particularly upset by the party’s policy on grammar schools.

The party responded by seeking to portray Sir Tom as unhappy at Mr Cameron’s attempts to reposition the party on the centre ground.

“There will always be a few people who feel uncomfortable with the changes that need to be made but now is not the time to abandon our strategy but to reaffirm it,” a Conservative spokesman said.

William Hague, the Shadow Foreign Secretary, echoed this, telling reporters: “Whenever you embark on a process of very serious change there are bound to be people who feel uncomfortable with it from time to time.”

His criticisms come after Lord Kalms, the party’s former treasurer, last month accused Mr Cameron of chasing less substantial policies and failing to provide a detailed policy programme. Stuart Wheeler, another substantial donor, has also called for a change in direction. He urged Mr Cameron last month to be clearer in advocating tax cuts and to develop a tougher approach on Europe.

Mr Cameron is less vulnerable to disaffection among party donors than his immediate predecessors, having broadened his funding base, creating a wider pool of backers prepared to give donations of £50,000.

But such attacks from long-time supporters illustrate the difficulties he has faced in trying to broaden the party’s appeal without alienating traditional Conservatives. They also continue the run of bad publicity that has dogged the Tory leader since the party’s poor showing in last month’s parliamentary by-elections and his trip to Rwanda as flooding hit the west of England.

Sir Tom, the life president of the transport group Arriva, donated £500,000 before the 2005 election and £25,500 in October last year, after Mr Cameron had been leader for almost a year. But he declared himself “very, very disappointed” with the state of the party under his leadership.

“The Tory party seems to be run now by Old Etonians and they don’t seem to understand how other people live. They seem to be very arrogant, like I suppose Old Etonians can be. They certainly don’t understand about grammar schools,” Sir Tom told The Guardian. He attended a grammar school in Sunderland and, although he left school at 15, said his education had made “all the difference” in his life.

The election watchdog suffered fresh embarrassment yesterday when a court rejected its request that the United Kingdom Independence Party forfeit more than £360,000 in donations. Instead the judge ordered UKIP to surrender only £14,500 from the donor involved, plus a further £4,000 from a separate source.

The ruling was a blow to the Electoral Commission, which brought the case in an attempt to demonstrate a more robust approach to its role in policing political donations. It has faced criticism for failing to act more decisively once Labour and the Conservatives were revealed to have bankrolled election campaigns using secret loans.

The UKIP case centred on donations from Alan Bown, a retired bookmaker from Kent, who has become the party’s biggest financial supporter. Mr Bown moved house but failed to add his name to the electoral register at his new address, making several donations he made to UKIP before the previous general election technically “impermissible”. The breach was ruled to be accidental.

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